Blight dragon

Ruin. Any creature that starts or enters within 25 ft of the blight dragon on its turn takes 10 (2d10) necrotic damage. 

Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws and can choose to use a life leech instead of one claw attack. 

Bite. Melee Weapon Attack: +8 to hit, reach 10 ft., 1 target. Hit: 14 (2d10 + 4) [piercing] damage plus 5 (1d10) necrotic damage. 

Claws. Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit: 10 (2d6 + 4) [slashing] damage.

Life leech.  RangedWeapon Attack: +8 to hit, range 15/50 ft., 1 target. Hit: 10 (2d6 + 4) [necrotic] damage and the dragon heals equal to the damage dealt. 

Tail. Melee Weapon Attack: +8 to hit, reach 15 ft., 1 target. Hit: 12 (2d8 + 4) [bludgeoning] damage.

Frightful Presence. Each creature of the dragon’s choice that is within 120 ft. of the dragon and aware of it must succeed on a DC 14 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to the dragon’s Frightful Presence for the next 24 hours.

Flaming shadow Breath (Recharge 5-6). The dragon exhales fire in a 60-foot cone. Each creature in that area must make a DC 15 Dexterity saving throw, taking 27 (9d6) fire damage and 27 (9d6) necrotic on a failed save, or half as much damage on a successful one.

The blight dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time, and only at the end of another creature’s turn. The blight dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 ft. of the dragon must succeed on a DC 15 Dexterity saving throw or take 10 (2d6 + 4) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

Dust storm (costs 3 actions). Each creature within 15 ft of the dragon must make a dc 15 con save or take 18 (3d12) necrotic damage and the creatures have disadvantage on attack rolls and checks until the end of their next turn.